Trolls filed 40% of patent infringement lawsuits in 2011

ARSTechnica: Trolls have long been the standard villain in patent debates. Often little more than an empty office in East Texas, patent trolls produce no useful products themselves but earn millions of dollars by threatening patent lawsuits against productive companies. There is plenty of anecdotal evidence that patent trolls are a serious and growing problem, but until recently there has been little hard data to back up the evidence.